Author: admin
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Path Independence of Conservative Forces
The primary test for determining whether a force is conservative or nonconservative is this: Let the force act on a particle that moves along any closed path, beginning at some initial position and eventually returning to that position (so that the particle makes a round trip beginning and ending at the initial position). The force is conservative only if…
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Work and Potential Energy
we discussed the relation between work and a change in kinetic energy. Here we discuss the relation between work and a change in potential energy. Let us throw a tomato upward (Fig. 8-2). We already know that as the tomato rises, the work Wg done on the tomato by the gravitational force is negative because the force…
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What Is Physics?
One job of physics is to identify the different types of energy in the world, especially those that are of common importance. One general type of energy is potential energy U. Technically, potential energy is energy that can be associated with the configuration (arrangement) of a system of objects that exert forces on one another. This is…
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Power
A contractor wishes to lift a load of bricks from the sidewalk to the top of a building by means of a winch. We can now calculate how much work the force applied by the winch must do on the load to make the lift. The contractor, however, is much more interested in the rate at which…
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Work Done by a Spring Force
We next want to examine the work done on a particle-like object by a particular type of variable force—namely, a spring force, the force from a spring. Many forces in nature have the same mathematical form as the spring force. Thus, by examining this one force, you can gain an understanding of many others. The Spring Force…
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Work Done by the Gravitational Force
We next examine the work done on an object by the gravitational force acting on it. Figure 7-6 shows a particle-like tomato of mass m that is thrown upward with initial speed v0 and thus with initial kinetic energy . As the tomato rises, it is slowed by a gravitational force ; that is, the tomato’s kinetic energy decreases because does work on the…
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Work and Kinetic Energy
Finding an Expression for Work Let us find an expression for work by considering a bead that can slide along a frictionless wire that is stretched along a horizontal x axis (Fig. 7-2). A constant force , directed at an angle to the wire, accelerates the bead along the wire. We can relate the force and the acceleration with…
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Work
If you accelerate an object to a greater speed by applying a force to the object, you increase the kinetic energy K (= mv2) of the object. Similarly, if you decelerate the object to a lesser speed by applying a force, you decrease the kinetic energy of the object. We account for these changes in kinetic energy by…
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Kinetic Energy
Kinetic energy K is energy associated with the state of motion of an object. The faster the object moves, the greater is its kinetic energy. When the object is stationary, its kinetic energy is zero. For an object of mass m whose speed v is well below the speed of light, For example, a 3.0 kg duck flying past us at 2.0 m/s…
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What Is Energy?
The term energy is so broad that a clear definition is difficult to write. Technically, energy is a scalar quantity associated with the state (or condition) of one or more objects. However, this definition is too vague to be of help to us now. A looser definition might at least get us started. Energy is a number…